The present invention relates to networked systems composed of a plurality of devices clustered for the exchange of data and control messages formatted according to predetermined protocols and, in particular although not essentially, to such systems where inter-device communication between some of the devices is via wireless link. The invention further relates to devices for use in groups or clusters to form such systems.
Networked interconnection of devices has long been known and used, starting from basic systems where different system functions have been provided by separate units, for example hi-fi systems or security systems having detectors, a control panel and one or more alarm sounders. A development has been the so-called home bus systems where a greater variety of products have been linked with a view to providing enhanced overall functionality in for example domestic audio/video apparatus coupled with a home security system and the use of telephone. An example of such a home bus system is the domestic digital bus (D2B), the communications protocols for which have been issued as standard IEC 1030 by the International Electrotechnical Commission in Geneva, Switzerland. The D2B system provides a single wire control bus to which all devices are interfaced with messages carried between the various devices of the system in a standardised form of data packet.
With all such domestic equipment interconnection schemes, there is a problem of connection to apparatus not supporting the communications protocols of the scheme. As an example, a user may have a music system comprising interconnected units such as a compact disc (CD) player, amplifier, tuner and cassette player which communicate with each other using a first set of communications protocols, together with an audio visual system comprising for example a television, video recorder and satellite receiver which communicate using a second set of protocols. In the absence of a certain degree of compatibility with existing systems, a user may be faced with having to replace many items at one time. One way to reduce this problem is to provide a gateway device which supports two or more sets of communications protocols and can “translate” messages between them, as described in U.S. Pat. No. 5,754,548 (Hoekstra et al), where D2B is used as a subsystem within a home electronic bus (HEB) system.
As is also described in U.S. Pat. No. 5,754,548, such gateway devices can be used as part of a link between two clusters of bus-connected devices supporting the same communications protocols, but with different protocols governing communications on the link between the clusters. The link between the clusters may, for example, comprise a wireless (infra-red or RF) channel between the two gateway devices, whilst the cluster devices themselves are hard wired to respective serial data buses.